<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
<style type="text/css">
	*{
		padding: 0;
	}
	div{
		clear: left;
		margin: 0 auto;
		width: 200px;
		border:1px solid red;
	}
	input{
		width:40px;
		height:40px;
		padding: 1px 6px;
		margin: 4px;
		float:left;	
		background-color:#ddd;
		
	}
	.str{
		width:122px;
		height:26px;
		padding: 6px;
		border:1px solid #ccc;
		margin: 4px;
	}
	
</style>
</head>
<body>
	<div>
		<div>
			<input type="text" class="str"/>
			<input type="button" value="C" />
			
		</div>
		<div>
			<input type="button" value="7" />
			<input type="button" value="8" />
			<input type="button" value="9" />
			<input type="button" value="/" />
		
			<input type="button" value="4" />
			<input type="button" value="5" />
			<input type="button" value="6" />
			<input type="button" value="*" />
		
			<input type="button" value="1" />
			<input type="button" value="2" />
			<input type="button" value="3" />
			<input type="button" value="-" />
		
			<input type="button" value="0" />
			<input type="button" value="." />
			<input type="button" value="=" />
			<input type="button" value="+" />
			<div style="clear: both"></div>
		</div>
	</div>
</body>
</html>